This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We developed a novel assay for measuring antibody titers in plasma capable of mediating antibody-dependent cell-mediated cytotoxicity against simian immunodeficiency virus infected cells.